Source of life and fundamental element for the body and health, water also helps prevent urinary tract disorders, pressure problems, water retention, constipation and fights skin aging, not to mention the effects on the brain . A paper just published in eBioMedicine concluded that adults who stay well hydrated appear to be healthier, develop fewer chronic conditions like heart and lung disease, and live longer than those who don’t get enough fluids. But how much water is needed?
There is no standard quantity
The recommendation to drink eight glasses a day (or two liters) is probably too much for most people, according to research published in the journal Science by the team of Yosuke Yamada, National Institute of Biomedical Innovation, Health and Nutrition in Japan. The study found that the measure varied widely with age, gender, activity levels, and immediate environment (see paragraph at the end, ed). «It has been estimated that i parameters are so many and variables so complex that it is not possible to establish a standard quantity for everyone – confirms Elena Dogliotti, nutritionist biologist, scientific supervisor for the Umberto Veronesi Foundation -. Not just in a general sense, but not even for the same person all year round. Water needs change according to gender, age, physical mass, lifestyle habits (sedentary lifestyle or not), climate, but also state of mind (stress can increase water production)».
Where did the eight glasses recommendation come from?
«People need indications: two liters are an average to prevent dehydration in every situation and subject. Moreover, drinking a lot is one of those pieces of advice that doesn’t risk causing harm even to those who would be fine with 700 ml of water a day».
What should an adult with a sedentary job do when it’s not too hot?
«In principle, the advice is: rehydrate in the morning by choosing a drink such as tea or milk (between 150 and 250 ml) and, if there was only coffee, remember to drink at least one glass of water. If you don’t feel thirsty during the morning, you can also avoid drinking, but you have to do it at lunch. The classic half-litre bottle (or a couple of glasses) is sufficient, to be finished in the office by the afternoon if there is leftover. Same thing in the evening. In this way we arrive at a liter and a half, two liters if we consider the food component».
How important is what we eat?
«It has a great impact, it is essential: it is better to favor fruit and vegetables and reduce salt (below six grams a day)».
Are there indicators of dehydration to look out for?
«If the urination is regular, keep in mind the urine color, which must be clear. Thirst already carries a signal of the onset of dehydration, so beware of the elderly and children in whom the thirst stimulus is reduced. In any case, increase water consumption in cases where the season or physical activity put you at greater risk”.
I study
A very rigorous Japanese study evaluated the water intake of 5,604 people aged between 8 days and 96 years from 23 countries. The peculiarity of the research was the way in which the scientists were able to measure how quickly water is consumed: the participants drank water spiked with deuterium, a stable isotope of harmless hydrogen, the elimination rate of which was calculated in detail. In this way the water exchange of each was determined (how much water do you consume per day), which directly reflects what the water requirement should be.
It has been seen that many people require only 1.5 to 1.8 liters per day and that the values depend on many external (environmental) and internal (physiological) factors. The highest values observed were those of men between the ages of 20 and 35, with an average of 4.2 liters per day. gives it between the ages of 20 and 40 had an average of 3.3 liters per day, which dropped to 2.5 liters at the age of 90. Under similar conditions, men consume about half a liter more water every day than women. Consumption decreases with age, increases in those who live in hot, humid climates and at high altitudes. Athletes and pregnant women consume more. Newborns have the highest turnover rate: they replace 28% of the water tank each day.
